1. Field of the Invention
The present invention relates to a method of improving the high-speed radial force variation of a pneumatic tire and a pneumatic tire having improved high-speed radial force variation.
2. Description of the Related Art
The radial force variation (RFV), radial runout (RRO) weight imbalance of a pneumatic tire are well known factors in tire vibrations during running, and they are mutually related to a high degree. Generally, various standards relating to tire uniformity tests such as the Japanese standard JASO C607-87 refer to the RFV and RRO measured at a relatively slow speed at which the centrifugal force can be disregarded (hereinafter low-speed RFV and low-speed RRO).
Even if such low-speed RFV and low-speed RRO and the weight imbalance at a relatively slow rotational speed are improved, there is still a possibility that vibrations occur during high-speed running over 80 km/h.
Thus, the inventor studied and found that a chief factor in the tire vibrations is the fundamental wave or harmonic of the RFV during high-speed running (hereinafter high-speed fundamental RFV).
Therefore, a primary object of the present invention is to improve the high-speed RFV of a pneumatic tire without affecting the low-speed RFV and RRO.
According to one aspect of the present invention, a tread portion of a pneumatic tire is provided on the radially inner surface with an elastic patch, the patch having a certain weight and being stuck at a certain circumferential position, the weight and position are determined based on (A) low-speed fundamental RFV or (B) low-speed fundamental RRO or (C) static weight imbalance of the tire, each measured before applying the patch.